The realization of electrical interconnecting contacts and vias is generally recognized as having an important role in the evolution of integrated circuits. Already with present state of the art integration technology of 0.35 .mu.m, the values of time constants (RC) (delays) attributable to the interconnection resistance and capacitance has risen above those intrinsic to the gate of an active component of the circuit. This situation is destined to worsen with the continuous reduction of the size of electronic devices. In addition, the complexity of integrated circuits will impose a drastic increase on the complexity of interconnecting. With the present materials, an analysis of a hypothetical 0.15 .mu.m technology would require ten interconnecting metal levels. This number is hardly compatible with the costs that would make such a technological development a viable one.
According to present industry trends, the development of integrated circuits demands the identification of new materials or structures capable of reducing the complexities of the required electrical interconnections. Eminently, the target is that of finding conductors of lower resistivity (p) than those presently in use, as well as dielectrics with a dielectric constant (K) lower than that of silica (SiO.sub.2) which is by far the most common dielectric used in integrated circuits and whose k is about 3.9.
To give a clearer picture of the simplification obtainable with new materials, it will be sufficient to realize that replacing Al with Cu for the metal layers and substituting SiO.sub.2 with a dielectric whose constant is K.ltoreq.2, would allow the implementation of a 0.15 .mu.m integration technology with only five interconnection metal levels, rather than the ten necessary with today's materials.
While the R&D hypothesis as far as the metallic materials are concerned identifies the use of copper as a way to achieve an appreciable improvement, it is in the field of the dielectrics where "targets" with a more accentuated margin of improvement than that obtainable through a reduction of the resistivity, have been identified. The development approaches of suitable dielectrics may be classified in three main groups.